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42.1 Background Highway agencies are implementing performance specifications in highway construction stan- dards to mitigate their risks. These specifications are based on construction- or material-related parameters known to relate to expected pavement performance. Although adoption of such speci- fications typically relax requirements on construction variables, specifications enable contractors to use different construction methods to achieve the desired pavement performance. As a result, the contractor undertakes certain risks and responsibilities associated with project construction. In the case of a substandard construction, a pay deduction may occur while payment incentives for the contractor can lead to quality work. Therefore, implementing performance specifications benefits all stakeholdersâagency, contractor, and road users. 2.2 Characteristics of Performance Specifications The construction specification has progressed over time based on specific needs. The follow- ing paragraphs briefly describe the features of both the method/prescriptive and performance specifications. Method Specifications Method specifications have the following characteristics (Scott et al. 2014a): â¢ They are well-established and easily understood. â¢ They are based on known or established materials and construction properties that can indi- rectly affect pavement performance. â¢ They restrict deviation of a particular property during construction. â¢ They lack built-in incentives for improving the final product. Examples of method specifications for pavement construction include mix design param- eters (e.g., air voids, binder contents, and percent passing a sieve size), compaction or density requirements, and level of surface smoothness. Although specifying such well-established meth- ods minimizes the risk associated with newer or less-proven procedures, it discourages the con- tractor from achieving more than the minimum requirements (i.e., the contractor only needs to meet these specifications during construction), whereas correcting performance deficiencies (if any) becomes the agency responsibility. Performance Specifications Performance specifications define the requirements of the end-product, thus allowing the contractor to select materials and construction techniques suitable for meeting the Process for Developing PRS Guidelines C h a p t e r 2
process for Developing prS Guidelines 5 requirements. The performance specifications can be classified into the following types (Scott et al. 2014b): â¢ End-result specifications (ERS) â¢ Quality assurance specifications (QAS) â¢ Performance-based specifications (PBS) â¢ Performance-related specifications (PRS) â¢ Warranties â¢ Long-term maintenance provisions End-result specifications allow the contractor to select a construction method to produce the final product, while the agency decides to accept or reject it. QA specifications require the contractor to perform quality management and acceptance activities throughout construction. Performance- based specifications (PBS) are QA specifications that describe fundamental engineering properties that can be used as performance indicators. For instance, specific ranges of resilient moduli of a pavement layer can be used to develop cracking or rutting performance models, including a com- bination of factors that represent traffic, environment, subgrade properties, and structural condi- tions. In contrast to PRS, PBS specify desired levels of actual engineering properties. PRS have the following additional characteristics (Scott et al. 2014a and 2014b): â¢ PRS incorporate key materials and acceptance quality characteristics (AQCs) that can be related to fundamental engineering properties used to predict performance. â¢ PRS are based on mathematical models which define desired AQC specification thresholds for acceptance testing during construction. â¢ PRS may provide rational pay adjustments based on the difference between as-designed and as-constructed life cycle costs or other statistically based quality measures. Warranties and long-term maintenance provisions often supplement performance specifications by providing thresholds or indicators that hold the contractor responsible for the quality of work for a period of time after project completion. Although method specifications are essential for defining the thresholds of certain variables in a project, several key advantages are associated with implementing PRS. The development of a PRS defines end-product performance based on desired outcomes and user needs. This provides a rational means for considering pay adjustments to the contractor through the mea- surement and evaluation of key performance parameters. The contractor can use different con- struction methods but accepts the associated risks. This can motivate a contractor to be more conscious of providing high-quality work that can exceed expectations and reduce the agency costs associated with construction inspection. In addition, the adoption of PRS requires the agency to relinquish control over some aspects of the work. Successful implementation of PRS can promote innovative construction methods and help achieve a high-quality end-product. 2.3 Performance-Related Strategy Several steps are required for the development of a performance-related strategy. These steps must relate user needs and project goals to the expected asset performance. The overall process should do the following (Scott et al. 2014b): 1. Identify user needs and project goals, 2. Relate needs and goals to performance indicators, 3. Consider the project delivery approach, 4. Determine the appropriate measurement strategy, 5. Establish incentive strategies and payment mechanisms (if needed),
6 performance-related Specifications for pavement preservation treatments 6. Identify deficiencies in strategy, 7. Identify and evaluate risks, and 8. Develop the specification. As part of this process, AQCs that could serve as performance indicators of a specific asset must be selected. A system of measurement along with verification methods must be established to evaluate these performance indicators. The measurement strategies will depend on the type of performance indicator, the type of project delivery method, and the defined performance lim- its. The PRS can be developed by evaluating historical performance data, reviewing the current standards, considering input from industry, analyzing findings from controlled test studies, and establishing relationships between quality characteristics and expected performance. Performance limits are incorporated into a quality assurance program to determine quality measures that appropriately assign incentives and disincentives (i.e., pay factors) depending on the quality of the completed project. Figure 2-1 (Scott et al. 2014b) shows a broad step-by-step process for develop- ing a performance-based strategy. Step 1: Identify User Needs and Goals The approach used to develop PRS shifts the emphasis from characterizing basic materials and construction procedures to focusing on the outcome of the project. This outcome should be aligned with the needs of the user; these needs are typically tied to functional performance issues (e.g., accessibility, safety, and ride quality). As such, PRS are suited for preservation treatments intended to address functional performance measures. Step 2: Relate Needs and Goals to Performance Parameters In terms of pavement preservation, common project goals include maximizing pavement performance by regularly applying treatments, minimizing delays caused by maintenance activi- ties, and increasing user safety by reducing pavement distresses. AQCs that relate to treatment performance characteristics (e.g., safety and ride quality) and affect these goals and user needs should be included in a specification because they are related to friction, pavement noise, and roughness. Step 3: Consider the Project Delivery Approach An essential step in developing a performance-related framework is to consider the delivery approach used for the project. High-level performance requirements control functional per- formance such as roughness, friction, and noise. On the other hand, low-level performance requirements control construction and material characteristics indirectly related to the expected performance. Generally, high-level performance requirements are not suitable for a delivery approach that requires a contractor to assume risk over items that cannot be controlled during construction (Scott et al. 2014b), such as the design-bid-build approach (DBB). In contrast, the design-build-operate-maintain approach (DBOM) requires that a contractor assume whole-life performance risks, including the monitoring and evaluation of performance over the service life of the project. The PRS must be tailored to the delivery approach by including the func- tional parameters used for monitoring and evaluating performance and allowing for flexibility in materials and construction requirements as agreed to by the agency and the contractor. Step 4: Determine the Appropriate Measurement Strategy The development of performance-related strategy requires the consideration of these key PRS components:
process for Developing prS Guidelines 7 â¢ Defining performance parameters and associated performance measures, â¢ Defining testing methods and sampling plans that evaluate compliance, and â¢ Using compliance test results in quality assurance programs. Each of these components must be determined through a detailed evaluation of candidate quality characteristics considered for inclusion in a performance-related specification. These characteristics depend on the parameter and treatment type. Section 2.4 presents an outline that examines the process for developing PRS guidelines. Step 1 Identify user needs and project goals Step 2 Relate needs and goals to performance parameters Step 3 Consider the project delivery approach Step 4 Determine the appropriate measurement strategy Step 5 Establish incentive strategies and payment mechanisms Step 6 Identify deficiencies in strategy Step 7 Identify and evaluate risks related to performance requirements Step 8 Develop the specifications Performance-Related Specfications From PRS Flow Chart Figure 2-1. Process for developing a performance-based strategy (Scott et al. 2014b).
8 performance-related Specifications for pavement preservation treatments Step 5: Establish Incentive Strategies and Payment Mechanisms A performance-related strategy that reduces costs (i.e., maintenance and repairs) for a project and provides incentives to the contractor for performing quality work would motivate a con- tractor to produce high-quality work. One such strategy is the use of performance-related pay adjustment factors that reflect the degree of compliance with specifications. Currently, there is no widely accepted method for calculating quality-related payment factors (Scott et al. 2014b). The following are two methods commonly used for calculating pay factors: 1. Life cycle cost (LCC) analysis of performance prediction models. This method is suited for use in developing pay factors because additions or deductions in pay are closely related to project construction and maintenance costs. Substandard construction can result in added costs for testing, maintenance, and rehabilitation. In contrast, construction that exceeds expected levels of quality can result in cost savings. The difference in the cost of as-designed compared to as-constructed pavement assets can serve as a basis for payment adjustment factors. 2. Statistically based sampling and testing plans used to measure variability. This method is regularly used to describe quality specifications that are primarily related to pavement con- struction. This type of measurement program produces a set of specifications based on laboratory-determined properties of field samples. The results are then used as a basis for acceptance and payment adjustment. This method provides a more practical approach for relating payment to the degree of quality of work (Scott et al. 2014b). An example of a sta- tistical measure of quality using the concept of percent within limits (PWL) is presented in Section 2.4. Step 6: Identify Deficiencies in Strategy The PRS measurement strategy must also be evaluated for deficiencies that may limit the extent of its implementation. Deficiencies may occur because of the unavailability of specialized or costly equipment or test results. Such factors must be identified and minimized to enhance implementation and adoption of a PRS. One method to address such gaps is to combine a PRS with prescriptive specifications to assist in describing performance (e.g., defining a range of chip seal construction emulsion rates that describe the effect on cumulative aggregate loss in addi- tion to evaluation of post-construction mean texture depth as a measure of expected raveling). Advancements in non-destructive testing (NDT) technology can also aid in collecting, process- ing, and evaluating data within a reasonable time frame. However, care must be taken to ensure that quality and performance of the end-product is not compromised. Step 7: Identify and Evaluate Risks This step identifies and evaluates the risks associated with the selected PRS levels. For example, there is always a probability that an agency would accept work that does not meet the require- ments or reject work that meets the requirement. This step will identify those risks and consider strategies to mitigate them. The following are key factors pertaining to risk assessment and man- agement (Scott et al. 2014b): â¢ Certain risks can affect the levels at which performance measures are specified. For instance, given that skid resistance and surface friction are functional performance measures (high- level) associated with user safety needs, the political sensitivity toward vehicle accidents and crash data may influence a shift in the PRS measurement policy of an agency. Instead of specify- ing a target skid resistance, an agency may choose to specify lower-level material and mixture properties expected to control surface friction.
process for Developing prS Guidelines 9 â¢ Upon identification of possible risks, the agency and contractor need to coordinate the assign- ment of risk responsibility. Potential scenarios under which a risk may manifest itself should be determined, and an appropriate risk management and monitoring strategy should be developed. A sound risk management strategy should promote understanding of the risks associated with a project and the selected PRS. The strategy should include a plan for addressing the risks in a manner that minimizes costs, meets project goals, and aligns with the needs of the agency, contractor, and roadway users. Step 8: Develop the Specification The final step in establishing a performance-based strategy is to develop a well-defined PRS. The PRS should indicate (1) the required level of performance, (2) criteria for evaluating the degree of compliance of the contractor, and (3) pay adjustments (positive or negative) associated with the degree of compliance. These items will differ, based on the delivery approach (e.g., DBB or DBOM) and selected PRS, but should include common elements (e.g., material and construction require- ments, quality assurance procedures, and payment adjustment programs). Developing a PRS is a part of the overall performance-based strategy. Available processes can be tailored to produce PRS for pavement preservation. The following section describes the process for developing a pavement preservation PRS. 2.4 Guidelines for PRS Development In developing PRS guidelines for pavement preservation treatments, the following items need to be addressed: 1. Evaluation of pre-existing pavement conditions for determining the suitability of a particu- lar preservation treatment for a given project. The effectiveness of preservation treatment depends on the treatment selection and timing. However, the timing and treatment type are significantly affected by the pre-existing condition of the pavement surface on which the preservation treatment is to be applied. Therefore, quantifying the pre-existing conditions in terms of remaining service life (based on existing distresses) or structural strength (e.g., based on deflection testing) is a key element for successful implementation of the PRS. 2. Identification of quality characteristics (i.e., material properties and construction variables) related to expected performance. The construction materials and methods may be unique to a preservation treatment, and performance measures may be more functional (i.e., only addressing the non-load-related surface conditions such as raveling, texture, and bleeding). 3. Development of a quality assurance and management program that incorporates sampling and statistical procedures to link variability in quality characteristics to expected performance and pay factor adjustments. Available procedures can be modified to account for performance limits unique to preservation treatments. The method for assessing pre-existing pavement conditions for selecting a treatment time and type needs to be specified. In this research, it was assumed that such methods are already established. Several quality characteristics will be identified in the list of preservation treatments presented in Chapter 3. The rationale for selecting quality characteristics for a specific preserva- tion treatment is presented in Chapter 5. In general, developing PRS for the preservation treat- ments involves requiring the following steps (see also Figure 2-2): 1. Select a preservation treatment. 2. Select candidate material and construction characteristics (i.e., quality characteristics) and performance measures.
10 performance-related Specifications for pavement preservation treatments Guidelines for PRS Development Step 1 Treatment Selection Step 2a Identify and Select Candidate AQCs (Variables/attributes for the treatment material properties and construction process which can be related to expected performance) Step 2b Identify Performance Measures (Functional or structural performance measures which can be explained by the AQCs) Step 3 Identify Relationships between AQCs and Performance Measure (Thresholds and Limits) Empirical relationships Mechanistic-empirical relationships Laboratory and field test approaches Step 4 Determine Thresholds and Limits (Quantify impact of variability on performance) Step 5 Identify Measurement of AQCs (Test methods in laboratory and field) Step 6 Select Sampling Protocols (Lot size, sample size, sampling frequency etc.) Step 7 Establish Quality Measurement Methods (PWL, LCC, other statistically based measures) Step 8 Develop Pay Adjustment Factors Validation and calibration of performance relationships and limits Defining new AQCs and performance relationships â¢ â¢ â¢ (Incentives and disincentives based on quality measures, quantify agency and contractor risks) Figure 2-2. Process for PRS development.
process for Developing prS Guidelines 11 3. Establish relationships between quality characteristics and performance measures and deter- mine performance limits. 4. Specify tests methods to measure the selected characteristics. 5. Establish a sampling and measurement plan. 6. Select quality measurement methods. 7. Develop pay adjustment factors for incentives and disincentives. Selection of Preservation Treatment The suitability of various flexible and rigid pavement preservation treatments was evaluated in terms of their ability to address functional pavement performance and the availability of construction- and material-related characteristics that can be measured and linked to expected pavement performance. Current practices in flexible and rigid pavement preservation were examined to determine commonly used quality characteristics for these treatments. Also, the state of the practice in preservation was reviewed to identify the criteria used for treatment selec- tion and optimum timing. Identifying AQCs and Performance Measures Once the pre-existing conditions of a pavement section have justified the use of a particular preservation treatment, the AQCs of that treatment must be evaluated to assess their relation- ship to expected performance. The literature defines three levels of PRS (Scott et al. 2014a, Scott et al. 2014b): â¢ Level 1 â âSimplifiedâ PRS. These specifications are defined by the standard agency monitor- ing and testing practices and emphasize the material and construction properties known to affect performance. Most of the current PRS developed by various highway agencies fall in this category. â¢ Level 2 â âTransitionalâ PRS. These PRS aim at better quantifying and comparing future per- formance from as-designed and as-constructed LCC analyses. Parameters measured under this PRS include NDT sampling and testing. â¢ Level 3 â âIdealâ PRS. PRS requires a thorough understanding of long-term material behavior and advancements in the NDT technology applicable to measuring related parameters. This PRS considers many performance-related AQCs measured by NDT methods in LCC analysis. Issues with the implementation of PRS (i.e., development or modification) related to the existing test methods must be addressed. The evolution of PRS development requires better understanding of the long-term per- formance related to the selected material or construction variable due to traffic and climatic effects. Further, the AQCs identified in preservation practices must be evaluated for their suitability to describe the functional performance of the selected treatments. A suitable PRS should demonstrate that the selected AQC can be used as a specification without exhibiting implementation-related gaps that can impede its adoption. Based on this requirement, the AQC should â¢ Affect pavement performance directly or in conjunction with other variables, â¢ Show established ability that demonstrates a relationship with pavement performance, â¢ Demonstrate an ability for a cost-effective and efficient measurement during construction, â¢ Capture construction variability. Any gaps for adoption of a specific AQC must be identified and addressed. The AQC cannot be a PRS candidate if the proposed method fails to overcome these gaps. A distinct separation
12 performance-related Specifications for pavement preservation treatments between pavement preservation and rehabilitation and reconstruction is needed for the follow- ing reasons: 1. The performance of preservation treatments significantly depends on the pre-existing pave- ment conditions. Therefore, the pre-existing pavement condition before applying a preser- vation treatment plays an important role in the future performance of the treatments. The pre-existing condition of an existing pavement entails both structural capacity and functional condition. 2. Given that preservation treatments are non-structural fixes, different performance measures should be considered for their functional performance evaluations. For example, texture, raveling, flushing, bleeding, and weathering are a few important indicators of performance for preservation treatments in flexible pavements. 3. The construction materials used in preservation treatments can be different than conven- tional pavement materials. For example, most of the preservation treatments for flexible pavements use asphalt emulsions or polymer-modified asphalt emulsions as compared to conventional asphalt or modified asphalt binders. 4. The construction processes used for preservation treatments are much different when com- pared to traditional pavement construction. For example, an important measure for chip seals success is the embedment depth of the aggregate, whereas compaction density is a mea- sure of success for traditional flexible pavement construction. Different performance measures for preservation treatments are documented in Chapter 3 and will be specified for the examples in Chapter 6 and Appendix A. Establishing AQC-Performance Relationships and Thresholds This step is critical in developing the preservation PRS framework and in establishing the suitability of PRS guidelines. The step establishes a relationship between the AQC and pave- ment performance for a specific preservation treatment. In developing these relationships, cer- tain ranges within the performance measure are correlated to threshold values of the selected AQC. Such correlation can be established by collecting and analyzing relevant data through the following: â¢ Analysis of performance-related trends in historical data from existing projects, â¢ Review of thresholds of AQCs and performance measures, â¢ Collaboration with industry members and practitioners, â¢ Application of engineering analysis and statistical modeling. Scarcity of available data (i.e., AQC and observed field performance) related to preserva- tion treatments is the main reason to propose a hybrid approach for developing relationships between AQCs and performance measures. The three approaches that follow will be used to develop examples that demonstrate a relationship between a candidate AQC and a particu- lar preservation treatment performance. These approaches are (1) empirical, (2) mechanistic- empirical, and (3) performance-based laboratory and field test properties. To demonstrate the application of these approaches, preservation treatments for both flexible and rigid pavements will be evaluated. Once the relationships between candidate AQCs and performance measures are established for the specific treatments, the limits or thresholds for the AQCs can be determined for the acceptable levels of performance. The specific guidelines used to develop PRS unique to each treatment are presented in Chapter 5 and illustrated by examples in Chapter 6 and Appendix A.
process for Developing prS Guidelines 13 Specify Test Methods Successful adoption of a PRS requires the use of an objective test method that can measure AQCs. Methods that provide quantitative results are preferable because the tests can be repeated to obtain the required information. Furthermore, test method specifications should consider the following concepts of rapid renewal: â¢ Minimizing the effect of user delays, â¢ Collecting and processing data in a timely manner, and â¢ Emphasizing NDT techniques. NDT, which focuses on evaluation of functional parameters, is especially important in developing PRS for pavement preservation treatments. Potential gaps in the selection of test methods include (1) the use of less-proven methods that may be deemed undesirable by a contractor unfamiliar with the associated calibration and analysis procedures and (2) the objectivity of manual measurement methods in comparison to automated data collection methods. These gaps must be considered as part of the overall perfor- mance-based strategy. The methods used must be agreed on by the agency and the contractor. Establish a Sampling and Measurement Plan A PRS must be supplemented by a sampling plan that balances efficiency with contractor and agency risks. Although extensive sampling plans may result in less risk to the parties involved, they may simultaneously accrue higher project and user costs. The plan should also be tailored to the type of AQC being tested, the resources available to the agency, and the goal of the project delivery approach. The variability of these factors means that sampling plans may be unique to each project. However, certain statistical sampling concepts recur, regardless of project needs (i.e., sample size, lot size, and sampling frequency). The type of parameter (i.e., an AQC) being tested will have the greatest effect on determining the sample size. For example, a testing parameter that uses predictive models will require more extensive testing than normally performed. This type of parameter would benefit more from a continuous rather than a point-based testing method and a sampling plan tailored to suit this measurement strategy. Lot size is dependent on project boundaries (e.g., lengths of pavement sections being surveyed, uniformity of pavement cross section, or similarity of material proper- ties). The project boundaries must be large enough that the surface conditions related to the PRS are described adequately, but not so large that it is impractical or inefficient to measure and process the data collected. Sampling frequency will also depend on the performance parameter, and the PRS should identify when and how often tests should take place (e.g., during the period of traffic restriction, during peak traffic times, periodically during construction, or immediately after construction). The testing frequency should be specified with the project goals and needs in mind. Sampling is discussed in detail in Chapter 4. Select Quality Measurement Methods Typically, an agency is responsible for choosing the quality measure to be used to evalu- ate compliance with a PRS. Statistically based quality measures are preferred, but traditional methods of evaluating averages or standard deviations do not address the variability inherent to measuring performance. Instead, methods such as PWL can be used as a quality measure that combines the sample average and sample standard deviation as an estimation of population
14 performance-related Specifications for pavement preservation treatments characteristics. By definition, PWL is the percentage of a lot that falls above a lower specification limit (LSL) but still lies below an upper specification limit (USL). Another measure of quality is percent defective (PD). This method is used as an alternative measure to PWL in the relation- ship: PWL = 100 â PD. However, the quality measure of PWL is used more often because of its ability to describe how much of the measured parameter is within specified requirements, rather than the PD method which describes the magnitude that failed to do so. Develop Pay Adjustment Factors Finally, another essential stage in PRS development is to provide a rationale for implementing contractor pay adjustments based on the quality of work provided. This step in developing PRS guidelines is parallel to Step 5 of the overall performance-based strategy. As discussed earlier, quality-related pay adjustment factors must be quantified using methods such as LCC analysis and statistically based sampling plans that measure the construction variability. The current state of the practice in calculating pay factors for pavement construction practices uses the concept of composite pay factors (CPFs) (Scott et al. 2014a). The value of a CPF is obtained through an additive approach using weighted pay factors from various acceptance parameters. This method is useful for a performance prediction model that incorporates numerous acceptance parameters as a basis of predicted performance. However, the weights used to determine CPF are subjective and may be difficult to defend. A well-developed pay adjustment plan should result in a bonus payment (i.e., incentive) to the contractor for work performed that exceeds the target performance level, or in reduced pay (i.e., disincentive) for substandard work. As part of evaluating the compliance criteria for awarding incentives and disincentives, the risks associated with acceptance should be considered: risk to the contractor (a) and risk to the agency (b). These risks cannot be eliminated, but a good plan can prevent an inordinate amount of risk from being placed on either the agency or the contractor. Computer simulation tools (e.g., OCPLOT and FHWAâs SpecRisk) have been developed to help evaluate the expected behavior of various acceptance plans and pay schedules by calculating and displaying operating characteristic (OC) and expected pay (EP) curves over a range of levels of con- struction quality (Scott et al. 2014a and 2014b). Numerous studies evaluated these risks further and, using the Monte Carlo method, demonstrated the significant influence of production and measurement variability, sample size, and bias on contractor risk simulation. A similar simula- tion method can be used to analyze the variables of a PRS measurement strategy, improve the pay adjustment plan, and reduce risks to the contractor. Chapter 4 present more information about these influences on risks. 2.5 Summary PRS are quality assurance specifications that describe the desired levels of material and con- struction quality characteristics that correlate with long-term performance of the finished product. The selection of PRS should be based on a combination of data availability and demon- strative ability to characterize performance. PRS should be amenable to acceptance testing at the time of construction and adhere to sound sampling and testing acceptance plans. Both the quality measures and thresholds used to describe the specifications and determine PRS compli- ance must be well-established. Lastly, payment mechanisms must be developed to provide a rational basis for pay adjustments to the contractor based on adherence to the specifications and expected performance of the end-product. Table 2-1 summarizes the various steps for develop- ing preservation PRS guidelines. The table highlights the specific requirement within each stage, along with a list of already-established general PRS processes and additional or alternative needs unique to preservation PRS.
process for Developing prS Guidelines 15 Stages 1. Selection of preservation treatment 2. Identifying AQCs and performance measures 3. Establishing AQC- performance relationships and thresholds Requirements Address pavement issues (distress types, severity, and extents) Consider existing conditions (treatment timings) Identify AQCs that can describe performance Distinguish between AQCs for rehabilitation and preservation Describe/justify PRS candidacy for preservation treatments Establish thresholds through performance-related relationships Adoptable Method Evaluate existing preservation treatments (i.e., treatment selection) Examine studies identifying key AQCs in construction practices, e.g.: o NCHRP Report 634 (PCC Texturing) o NCHRP Synthesis 342 (Chip seal) o NCHRP Synthesis 411 (Microsurfacing) roads) o SHRP2-S2-R26-RR- 2 (Guidelines for preservation of high- traffic-volume AQC-performance: o Analysis of performance- related trends in historical data o Review thresholds and performance measures o Collaboration with industry and practitioners o Application of engineering analysis and statistical modeling Adjusted Method Treatment should improve functional pavement performance Preservation AQCs should: o Impact pavement performance o Show ability to relate AQC with functional pavement performance o Be measurable during construction o Capture construction variability Establish thresholds for the AQCs unique to the preservation treatments Approaches: o Empirical o Mechanistic- Empirical o Performance- based lab and field test evaluations 4. Specifying test methods 5. Sampling and measurement plan Test method should be objective Quantitative results are preferable for repeatability The test procedure will be unique to the parameter being measured Tailored to the type of parameter being measured Consider agency resources and project delivery approach Sample size, lot size, sampling frequency Examine common testing methods in highway construction Select methods based on ability to measure parameters of interest (consider NDT techniques) Lot-by-lot sampling strategy is common practice and decided on by project engineer and agency Project boundaries govern lot size Acknowledge provisions that may be needed for tests not commonly used that may require advanced training and accrue costs Method should be aligned with rapid renewal concepts: o Minimize user delays o Timely data collection o NDT techniques Frequency is unique to parameter being tested and should be specified with the project goals in mind (continued on next page) Table 2-1. Process for preservation PRS development.
16 performance-related Specifications for pavement preservation treatments 6. Selection of quality measurement methods Two common quality measures: o LCC analysis of performance prediction models o Statistically based sampling and testing plans measuring variability Statistically based methods for pay adjustment factors more common (e.g., PWL) AASHTO R-9, R-10 provide standards for quality and statistics used in acceptance plans for highway construction Stages Requirements Adoptable Method Adjusted Method Use these methods and relate to the relationships determined from data analysis to define AQLs and RQLs unique to preservation PRS 7. Develop pay adjustment factors Pay factors provide rationale for pay adjustments Determine pay factors using analysis of LCC or statistical sampling Evaluation of risks associated to contractor and agency Evaluation OC and EP curves over a range of levels of construction quality Use of MCS method to show impact of variability, sample size, and bias on contractor risk Methods used to develop pay factors and evaluate risks are established in standards and common agency practice Use the statistical analysis and AQLs/RQLs developed to determine ranges of PRS and associated pay factors and impact on contractor and agency risk Justify the pay adjustments with expected performance for preservation treatments Table 2-1. (Continued).